The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Internal combustion engines combust an air/fuel (A/F) mixture within cylinders to drive pistons and generate drive torque. A ratio of air to fuel in the A/F mixture may be referred to as an A/F ratio. The A/F ratio may be regulated by controlling at least one of a throttle and a fuel control system. For example, the A/F ratio may be regulated to control torque output of the engine and/or to control emissions produced by the engine.
The fuel control system may include an inner feedback loop and an outer feedback loop. More specifically, the inner feedback loop may use data from an exhaust gas oxygen (EGO) sensor located upstream from a catalytic converter in an exhaust system of the engine system (i.e., a pre-catalyst EGO sensor). The inner feedback may use the data from the pre-catalyst EGO sensor to control a desired amount of fuel supplied to the engine (i.e., a fuel command).
For example, the inner feedback loop may decrease the fuel command when the pre-catalyst EGO sensor senses a rich A/F ratio in exhaust gas produced by the engine. Alternatively, for example, the inner feedback loop may increase the fuel command when the pre-catalyst EGO sensor senses a lean A/F ratio in the exhaust gas. In other words, the inner feedback loop may maintain the A/F ratio at or near an ideal A/F ratio (e.g., 14.7:1 for gasoline engines).
The outer feedback loop may use information from an EGO sensor arranged after the catalytic converter (i.e., a post-catalyst EGO sensor). The outer feedback loop may use data from the post-catalyst EGO sensor to correct (i.e., calibrate) an unexpected reading from the pre-catalyst EGO sensor, the post-catalyst EGO sensor, and/or the catalytic converter. For example, the outer feedback loop may use the data from the post-catalyst EGO sensor to maintain the post-catalyst EGO sensor at a desired voltage level. In other words, the outer feedback loop may maintain a desired amount of oxygen stored in the catalytic converter, thus improving the performance of the exhaust system.